Positron API for capturing console output

[kv9898]

I have just startef to write an extension for R package management in Positron to mimic the functionality in RStudio. My initial thought was that if we could execute R code in console and capture the output, it shouldn't be too hard to put this together. While I found in positron.d.ts the API call to execute code (positron.runtime.executeCode), I didn't find one for capturing the result output. Any suggestions?

[juliasilge]

We have talked about this quite a number of times, but have always found other ways to work around needing the output itself. Right now the proposal we are most seriously considering is #2622, which is about getting something back from positron.runtime.executeCode like whether the code finished, whether it errored, whether the runtime restarted, etc.

Want to take a look and see if that proposal could fit your use case?

[kv9898]

We have talked about this quite a number of times, but have always found other ways to work around needing the output itself. Right now the proposal we are most seriously considering is #2622, which is about getting something back from positron.runtime.executeCode like whether the code finished, whether it errored, whether the runtime restarted, etc.

Want to take a look and see if that proposal could fit your use case?

Sounds very similar to what I was looking for! Guess I need to pause my extension project then. I wonder if I can retrive the path of the active R session, which may provide a workaround?

[juliasilge]

I think what might provide the most useful workarounds for now is to check out how we set up various commands:
https://github.com/posit-dev/positron/blob/main/extensions/positron-r/src/commands.ts

Especially the command for r.packageInstall:

positron/extensions/positron-r/src/commands.ts

Line 69 in e809c1c

vscode.commands.registerCommand('r.packageInstall', async () => {

What this command does is:

• install the local workspace package in the terminal via a task
• focus the console when that is done
• restart the console
• after the console has restarted, do library(package_name) to load it

I think that will give you some helpful patterns for how to approach your use case in the current state of the Positron API.

[kv9898]

That's very useful! However, I would also want the package manager to list all installed and loaded packages of the console. This now seems a bit difficult to achieve with the current API?

[juliasilge]

The internal, built-in R extension does have a way to do this that you might look at. Check out the method here for whether an R package is installed:

positron/extensions/positron-r/src/session.ts

Line 433 in 20eeaf5

public async packageVersion(

And this method for whether the package is attached:

positron/extensions/positron-r/src/session.ts

Line 572 in 20eeaf5

async isPackageAttached(packageName: string): Promise<boolean> {

I believe that an external extension would be able to take a similar approach with the RPC calls, but in full disclosure, you would be the first person to try to build on these methods. If you are up for it, give it a go and please come back with any questions you have as you try it out!

[kv9898]

@juliasilge I noticed that there was a recent update with the executeCode api, but I did not end up using it, for two reasons:

1. It does not capture the printed output when the code is executed in the silent mode.
2. (correct me if I'm wrong), R omits information in console output if it is too long (typical for R installed package information).

In the end, my solution is to output the information to a temp JSON file, which is to be read by my Positron extension. Currently, the development version is able to read the installed and loaded packages, load/unload them, and jump to the help topic when the names are clicked. I think it might be useful if I add package installation/uninstallation/updates. My current plan is to mimic RStudio behaviour as much as possible. Any suggestions?

WeChat_20250404012832.mp4

[jmcphers]

You're right, this API is not really designed to do what you are trying to do. I took a stab at describing the API I think would be needed to accomplish this: #7112